\\[-1.8ex] Soil Heterogeneity & 0.770$^{***}$ & 0.816$^{***}$ & 0.501$^{***}$ & 0.494$^{***}$ & 0.439$^{***}$ & 0.364$^{**}$ \\ 
  & (0.158) & (0.159) & (0.159) & (0.160) & (0.160) & (0.158) \\ 
  & & & & & & \\ 
\\[-1.8ex] 
Observations & 3,109 & 3,109 & 3,109 & 3,109 & 3,109 & 3,090 \\ 
R$^{2}$ & 0.013 & 0.155 & 0.235 & 0.237 & 0.268 & 0.315 \\ 
